Miniature radio transmitters worn on the person are known for the purpose of summoning police or medical aid in case of emergency. Such a transmitter may have a range of 100 or 200 m, and may form a part of a system that includes a receiver which is adapted to activate an alarm or a telephone dialing device.
The transmitter itself is preferably worn on the person, as by a neck strap or cord, and may be about the size of a paper match book or a cigarette lighter.
Ordinary switches are not suitable for activating such a transmitter. A toggle switch for example requires two hands, one to hold the transmitter and the other to flip the switch. Ordinary push-button switches are susceptible to false operation when the wearer leans against an object or, in the case of a cardiac patient, turns over in bed.
A switch means is needed which is operable with one hand, requires little space, cannot be operated by pressures incident to normal activities, and is operable silently in a concealed manner.